1. Technical Field
This invention relates to lasers and more particularly to an air cooled laser tube made up of a plurality of uniquely constructed segments.
2. Background Art
Both segmented and non-segmented laser tubes are known. It is also known to cool the laser tube with either air or a liquid such as water. For example, applicant's prior U.S. Pat. No. 4,774,713 teaches an air cooled laser tube having external fins. The tube is formed of relatively short segments with the bore of the tube being defined by ferrules supported within the segments by pairs of cup-like metal supports. A water cooled non-segmented tube is illustrated in U.S. Pat. No. 4,734,915 and with internally spaced discharge confining elements. U.S. Pat. No. 4,764,932 provides another example of an essentially solid tube with liquid cooling. Applicant's U.S. Pat. No. 4,553,241 teaches another type of air cooled, segmented laser tube in which the discharge confining elements are in the form of refractory metal discs supported within relatively short segments.
In the art of air cooled segmented laser tube constructions, alumina has been used to form the tube but has the disadvantage of poor thermal conductivity. For air cooled tubes having external fins, beryllia provides a better thermal conductivity. A tube formed of beryllia also facilitates transferring heat axially in those areas where the air cooling fins on the exterior of the tube are necessarily spaced apart to provide proper air flow. Experience with the air cooled, segmented tube construction shown in U.S. Pat. No. 4,553,241 has lead to the recognition that while both the disc system of U.S. Pat. No. 4,553,241 and the ferrule system of U.S. Pat. No. 4,774,713 have demonstrated advantages over the solid tube-type construction, there is a need for an improved air cooled laser tube construction which permits the use of relatively long segments to facilitate the mounting and efficiency of external air cooling fins and to minimize the number of sealed connections between segments. The use of relatively long segments in water cooled tubes is known to reduce electrolysis and provide an acceptable electrical isolation. The sought for improved air cooled tube construction would also ideally mount a series of suitably cooled, discharge confining ferrules or discs within each of a plurality of relatively long segments. However, the art has not heretofore provided an air cooled laser tube construction permitting a plurality of discharge confining ferrules or discs to be mounted in each of several relatively long segments making up the overall tube.
When disc supports are brazed within a long, water cooled tube formed of alumina as in U.S. Pat. Nos. 4,378,600 or 4,734,915, it will be apparent that the internal diameter of the tube must be large enough to house the cathode. Therefore, efficiency is necessarily reduced and cost is added as compared to using a smaller, more efficient tube. Brazing of the discharge confining disc to beryllia cannot be achieved though it might be desirable and assembly of the numerous disc subassemblies within the relatively long tube is difficult.
With the foregoing in mind, the primary objective of the present invention is to provide a further improved air cooled segmented laser tube construction which permits use of relatively long segments and discharge confining ferrules. While primarily concerned with providing an improved air cooled segmented laser tube, the construction of the invention lends itself to water cooling as later described. Other objects will become apparent as the description proceeds.